Self cooling container

ABSTRACT

A container that comprises first and second sidewalls and first and second end walls connected to a base. At least one of the base, respective sidewalls, or respective end wall is formed of a material that has a high thermal conductivity. At least each of the sidewalls or each of the end walls may be provided with venting to promote air flow. The first and second end walls and the first and second sidewalls are pivotally connected to the base.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority benefit under 35 U.S.C. §119(e) to U.S. Provisional Application No. 61/260,256, filed Nov. 11, 2009 in its entirety.

BACKGROUND OF THE INVENTION

This present invention relates to a multi-purpose container for storing and transporting goods. More particularly, the present invention relates to a multi-purpose container for maintaining temperature of the produce container at a temperature of a cooling medium contained therein to preserve perishable items shipped by produce container.

Containers for storing and transporting perishable items such as produce have been used in the fruit and vegetable marketing industry, by way of example for many years. At the outset, wooden boxes were used. However, they suffered from many well documented disadvantages. Over time, the industry adopted containers made of plastic materials because of their light weight, durable characteristic.

These containers are provided with vent holes for air circulation in order to cool the perishable items contained therein. The prior art, however, did not address the question of efficient and uniform cooling throughout the entire container or uniform cooling when multiple containers are stacked one upon the other.

One such proposed solution is known from U.S. Pat. No. 5,727,711, which is incorporated as if fully set forth herein. The disclosed produce container (also herein a crate) included a plurality of openings of specific dimensions in the floor. Each of the sidewalls also includes a plurality of openings of specific dimensions. Furthermore, the sum of the area occupied by the openings occupy a specific percentage of the area of the wall. This solution does provide a satisfactory convection cooling technique, however, it relies upon the passage of the air or other fluid through the container and requires specific vent hole dimensions and ratios which must be maintained within some criticality.

Furthermore, even during transport when chilling is provided by a fluid medium, such as water or air, the produce may also be packed in ice to minimize spoilage. Therefore, there is also a need for a container to facilitate the chilling effect of the ice while minimizing the loss of ice. However, the prior art system relies heavily on air circulation to accomplish its solution.

Furthermore, prior to use in the field, crates are usually stored out in the field or in a warehouse where they take on the ambient temperature of the environment over time. As they are used in the field, they are often much warmer than the system needs to be. Thus, there is the necessity for the use of ice or other cooling fluids. However, there is much thermal inertia in the crate so that much of the cooling capacity of the ice is wasted on the crate which has a tendency to raise the overall temperature of the environment within the crate which may lead to premature spoilage of the produce within the crate. It is desirable to lower the temperature of the produce as quickly as possible to minimize the spoilage.

Therefore, there is a need for a container which addresses the shortcomings of the prior art.

SUMMARY OF THE INVENTION

The present invention relates to a durable container for storing and transferring perishable goods, such as crops, fruits and vegetables from the field to the market. More particularly, the present invention relates to a reusable stackable container which is adapted to provide efficient uniform cooling.

In accordance with the present invention, a produce container has a floor and four adjoining vertical portions, made up of opposite end wall pairs and opposite sidewall pairs. At least the walls are formed from a material having a high thermal conductivity, i.e. low thermal inertia.

In a preferred embodiment, the crate is a collapsible, reusable container for carrying goods such as produce. The container includes four hinged walls and a base. The walls include two end walls and two sidewalls. These walls can be folded down onto the base so that the container assumes a flat configuration for easy storage. When unfolded, the walls are properly aligned and securely locked together so that they provide a rigid container that can be stacked with other similar containers.

In another embodiment of the invention, the first sidewall may include at least one latching member that cooperates with a latching member of the first end wall to secure the first sidewall and the first end wall together when the first sidewall and the first end wall are in upright positions. The container may also include a wall locking system that has a plurality of locking members on the first sidewall and at least one locking member on the first end wall. The locking member on the first end wall cooperates with the locking members on the first sidewall to prevent the first sidewall from moving relative to the first end wall in at least one direction when the first sidewall and first end wall are in upright positions. The container may also include a wall alignment system that has a first member extending from one of the sidewalls, and a second member that extends from one of the end walls. According to the present invention, the first and second members of the wall alignment system cooperate to align adjacent sidewalls and end walls before the sidewalls and end walls achieve a completely upright position.

In an alternative embodiment, vent holes are formed in at least one of opposing sidewall pairs and/or opposing end wall pairs. Air flow is facilitated through the vents.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of a collapsible container according to the present invention;

FIG. 2 is a perspective view of a base as shown in FIG. 1;

FIG. 3 is an outside perspective view of a sidewall having a contoured upper surface according to the present invention;

FIG. 4 is an inside perspective view of the sidewall shown in FIG. 3;

FIG. 5 is an elevational view of the outer surface of the sidewall shown in FIG. 3;

FIG. 6 is an elevational view of the inner surface of the sidewall shown in FIG. 4;

FIG. 7 is an end view of one of the sidewalls of the container shown in FIG. 1;

FIG. 8 is an end view of the other sidewall of the container shown in FIG. 1;

FIG. 9 is an outside perspective view of an end wall according to the present invention illustrating an outer surface of the end wall;

FIG. 10 is an inside perspective view of an end wall according to the present invention illustrating an inner surface of the end wall;

FIG. 11 is an elevational view of the inner surface of the end wall shown in FIG. 10;

FIG. 12 is an end view of one of the end walls shown in FIG. 1;

FIG. 13 is a cross-sectional view through one of the end walls shown in FIG. 1;

FIG. 14 is an elevational view of the outer surface of the end wall of FIG. 9;

FIG. 15 is a perspective view of the container shown in FIG. 1 wherein the combined height of the folded sidewalls, shown in FIGS. 3-6, is greater than the width of the base;

FIG. 16 is a perspective view of another embodiment of the container according to the present invention wherein the combined height of the folded sidewalls is less than the width of the base; and

FIG. 17 is a perspective view of the embodiment illustrated in FIG. 16 with the sidewalls in an upright, raised position.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a collapsible container or crate 10 according to the present invention. Collapsible container 10 can be used to store or transport goods. Container 10 is particularly suitable for transporting produce such as fruits and vegetables, where use of cooling fluids such as air or gas, as well as ice, are necessary to keep the produce fresh and consumable until it reaches a predetermined destination such as a market. The container 10 is formed of a plastic material by injection molding or other known plastic molding processes that are suitable for forming reusable, collapsible containers.

The plastic material has a high thermal conductivity. For the purposes of this application, high thermal conductivity is a thermal conductivity substantially greater than that of conventional crate polypropylene (0.22 W·K⁻¹·m⁻¹), and preferably at least about 0.30 W·K⁻¹·m⁻¹ to 1.2 W·K⁻¹·m⁻¹; and in one embodiment 0.55 W·K⁻¹·m⁻¹ and 0.75 W·K⁻¹·m⁻¹. One such material is a polypropylene or mixed with exfoliated graphite. High density polyethylene (“HDPE”) having a thermal conductivity of 0.39 W·K⁻¹·m⁻¹ to at least 0.8 W·K⁻¹·m⁻¹ may also be used. In this embodiment, the high thermal conductivity material is HDPE mixed with exfoliated graphite. The thermal conductivity is a function of the percentage of graphite within the mixture. In a preferred embodiment the graphite may be included at between about five percent to thirty five percent by weight; and in one embodiment between eight percent and thirty percent by weight. In an alternative embodiment high density polyethylene may be used as the base material.

Container 10 comprises a base 14, sidewalls 34, 36 and end walls 44, 46. As shown in FIG. 1, each of these walls has a handle opening so that the container can be easily carried. The base 14 includes a bottom panel 15 that forms a lower support surface for carrying and supporting the goods positioned within the container 10. Like the overall shape of the container 10, bottom panel 15 is generally rectangular in shape. However, the container and base can have any shape such as substantially square or substantially oblong. Alternatively, the sidewalls 34, 36 can be substantially straight and the end walls 44, 46 can be slightly curved, or vice versa. Additionally, the container can be of any size. As shown in FIGS. 14 and 15, the container 10 can have sidewalls 34, 36 that are any height above the base 14 and any length.

Providing a base and walls having a high thermal conductivity, facilitates cooling of the crate and its environment more rapidly than the prior art polypropylene crates. The crate adopts the temperature of the cooling medium such as a refrigerating fluid or ice more rapidly to provide a cold environment for any perishable goods. However, in a preferred embodiment, base 14 may be formed with vent opening 600 therein, sidewalls 34, 36 may be formed with vent openings 800 therein, and end walls 44, 46 may be formed with vent holes 700 therein to promote cross ventilation of a cooling fluid such as air. It follows, that at a minimum, the vent openings provided in a posed wall pairs to promote flow of the air or other cooling medium across the crate.

In a preferred embodiment, the holes are designed as taught in U.S. Pat. No. 5,727,711 to promote efficient thermal transfer from fluids traveling through the crate.

As shown in FIG. 2, the base 14 has two opposed side edges 16 and 18, and two opposed end edges 20 and 22. The base 14 further includes upwardly extending base wall sections 24 and 26 that extend parallel to the end edges 20, 22 and perpendicularly away from the bottom panel 15. These base wall sections 24, 26 can be integrally molded with the base 14. Each wall section 24, 26 has an upper edge 25 for supporting either the sidewalls 34, 36 or the end walls 44, 46 depending upon which set of walls is intended to be folded over the base 14 last and unfolded first.

As shown in FIG. 1, the opposed sidewalls 34 and 36 extend along the length of the base 14 on opposite sides of the bottom panel 15. The sidewalls 34 and 36 are each pivotally attached to bottom panel 15 by a hinge system 37 that is located along the opposed side edges 16, 18 of bottom panel 15. The hinge system 37 permits the sidewalls 34, 36 to be pivoted toward, or away from, the bottom panel 15 along edges 16 and 18 so that they can be positioned in either an upright, unfolded position in which it extends perpendicular to the base 14, or a horizontal, folded position where it extends parallel to the base 14.

As seen in FIGS. 1-2, the hinging system 37 along each side of the container 10 includes a plurality of rod sections 38 that extend across a portion of each sidewall 34 and 36. The outermost rod sections 38 are spaced inwardly from the end surfaces 91 of the sidewalls 34 and 36 proximate end walls 44, 46. In one embodiment, the rod sections 38 are formed integrally with the base 14. In an alternative embodiment, the rod sections 38 are joined together as a single member that extends along the entire length of the hinge and through adjacent supports in the base 14. The ends of the single member 38 are supported by the outermost supports.

The hinging system 37 on each side of the container 10 also includes hinge members 39 that extend downwardly from sidewalls 34 and 36 and into openings in the bottom panel 15, as shown in FIGS. 1 and 3-6. The hinge members 39 can be integrally molded to, or otherwise unitarily formed with, their respective sidewall 34, 36. As shown in FIGS. 4 and 7-8, each hinge member 39 has a C-shaped cross-section that receives and partially surrounds a respective rod section 38. Each hinge member 39 rotates about its respective rod section 38 so that the sidewalls 34 and 36 pivot and fold with respect to bottom panel 15 with minimal wearing of hinging mechanism 37.

In an alternative embodiment, the hinge members 39 can be secured to their respective rod sections 38. In this alternative embodiment, the rod sections 38 rotate relative to the base 14 instead of the hinge member 39 rotating relative to the sections 38. This hinging system 37 can also be used to hingedly connect the end walls 44, 46 to the base 14, as discussed further herein.

As shown in FIGS. 2-4, the hinging system 37 does not extend the full length of base 14. Instead, the hinging system 37 terminates a distance away from the end surfaces 91 of each sidewall 34, 36 to permit easy pivoting of the sidewalls and to reduce the damage that may occur to the hinges if they were placed in close proximity to the ends of the sidewalls. Additionally, the hinging system 37 terminates at points that are spaced from the end walls 44, 46 by pockets 62 that are proximate the end walls 44, 46. This spacing eliminates the need for extending the hinging system into pockets 62 or between these pockets 62 and the end walls 44, 46. As a result, the pockets 62 are able to be spaced along the container 10 so they can receive cooperating stacking tabs 58 from other containers, including corrugated boxes, as discussed below. This distance between the hinge system 37 and the end walls 44, 46 could be any distance that is known in the industry for pockets 62 that receive stacking tabs 58. In order to stabilize the sections 93 of the sidewalls 34, 36 that extend between the hinge system 37 and the end walls 44, 46, the sidewalls 34, 36 and the bottom panel 15 include a wall stabilizing system 80, seen in FIGS. 1, 15 and 16. By stabilizing and limiting the inward movement of the wall section 93, the goods carried by the container 10 are protected against the damage caused by conventional, unrestrained sidewalls.

The stabilizing system 80 include a plurality of stabilizing members 81 positioned along the sidewalls 34, 36 and a plurality of cooperating stabilizing members 82 positioned along the side edges 16, 18 of the bottom panel 15. In a preferred embodiment, the stabilizing members 81 include a plurality of projections or pegs that extend from a lower surface of the sidewalls 34, 36 as shown in FIGS. 5-8. The stabilizing members 82 include holes in the bottom panel 15 (shown in FIG. 2) that are aligned with the members 81 in order to receive the projections 81 as the sidewalls 34, 36 are being moved into their upright position. When the projections 81 and holes 82 are mutually engaged (when the sidewalls are partially or completely upright), they provide support, stability and strength (structural rigidity) to the end sections 93 of the sidewalls 34, 36. The structural rigidity added by the stabilizing system 80 and the limited movements of the corners enhance the stacking strength of the container. As shown in FIGS. 2 and 5-6, the projections 81 and holes 82 are only located between the outermost hinge member 39 and the end surfaces 91 of the sidewalls 34, 36 that extend along the end walls 44, 46. The projections 81 and openings are located only along section 93. Members 81, 82 are not positioned between adjacent hinge members 39 because the hinge members 39 provide sufficient stability along the middle portion of the sidewalls 34, 36. In an alternative embodiment, the holes 82 could be formed in the lower surface of the sidewalls 34, 36 and the projections 81 extend upwardly away from an upper surface of the bottom panel 15. Also, holes 82 include open holes or recesses with side and bottom walls.

Like sidewalls 34 and 36, end walls 44 and 46 are similarly pivotally attached to the bottom panel 15 by way of a hinging mechanism 48 which is similar in structure to hinging mechanism 37 described above, as shown in FIG. 1. However, unlike the sidewalls, the end walls 44, 46 are folded relative to base 14 at a distance remote from the bottom panel 15. Particularly, end walls 44 and 46 are pivotally attached to upstanding wall sections 24 and 26, respectively, of the bottom panel 15, proximate upper edges 25. The height of the upstanding wall sections 24, 26 is chosen based on the required distance from the bottom panel 15 that the walls 44, 46 must be spaced in order to fold over the folded sidewalls 34, 36 and form a stackable structure with a flat upper surface. As with the sidewalls 34, 36, the end walls 44 and 46 are able to achieve a folded position and an upright position.

As discussed above, the hinging system 48 used for end walls 44, 46 is similar to that described above in association with sidewalls 34 and 36. This system 48 is illustrated in FIGS. 1, 9. The system 48 includes a plurality of rod sections 38 and C-shaped hinge members 39 with internal bearing surfaces, as shown in FIGS. 9 and 12-13. As with hinging mechanism 37, in a preferred embodiment hinging mechanism 48 does not extend to corner line 31 but is remote therefrom. Also, the rod sections 38 can be part of a single rod or they can be separate, independent sections. Moreover, either the hinge members 39 or the hinge members 39 and the rod sections 38 rotate relative to the base 14 when the end walls 44, 46 are unfolded. When the hinge members 39 rotate relative to the base 14, they rotate within an opening 45 that includes pivot limiting members 88. These members 88 prevent the end walls 44, 46 from pivoting past about 90 degrees relative to the bottom panel 15 (past vertical).

As best shown in FIG. 10, each end wall 44 and 46 has a U-shaped horizontal cross section that is formed by a main end wall portion 50, and two shorter flange portions 52. In a preferred embodiment, these wall portions are integrally formed together as a single unit. The flange portions 52 extend from either side of portion 50. Additionally, the flange portions 52 are oriented orthogonal to main end wall portion 50 and, when the container is assembled, they extend in the direction of the sidewalls 34 and 36.

Referring now to FIG. 1, the collapsible container assembly 10 also includes locking system 64 for securing the sidewalls 34, 36 to the end walls 44, 46 and stabilizing the corners. Moreover, the locking system prevents the sidewalls from moving relative to the end walls in at least the vertical direction and the rotational direction that is past vertical. The locking system 64 provides interlocking engagement between the sidewalls 34, 36 and the end walls 44, 46 when these walls are in their upright position. In a preferred embodiment, the locking system 64 forms dovetail joints at each of the corners with the cooperating elements 66, 67, 68, 69 of the joints forming only a fraction of their respective walls. For example, each cooperating element may be one-half the thickness of the walls. Alternatively, one element may be one-third or one-quarter the thickness of its wall while the cooperating element is two-thirds or three-quarters the thickness of its wall, respectively. No matter their size, the cooperating elements of the joints are hidden from any line of sight when the container is fully assembled and the walls are in their upright positions. The advantages to these joints are discussed above.

The locking system 64 includes flanges 54 at the outer ends of the sidewalls 34, 36 proximate the surfaces 91, and the flanges 52 on the end walls 44, 46. As shown in FIG. 3, the side of each flange 54 that is opposite the interior of the container 10 includes at least one locking tab 66. In a preferred embodiment, each flange 54 includes a plurality of locking tabs 66 disposed at predetermined spaced intervals by gaps 67. Each locking tab 66 has a substantially triangular shape with the largest portion of the tab 66 extending along edge 91. Each tab 66 also includes first and second locking surfaces 72, 74 that extend between the outermost surface 70 and the main portion of sidewalls 34, 36.

Referring to FIGS. 10 and 13, each flange 52 includes at least one tab receiving opening 68 that receives the tab(s) 66 on one of the flanges 54. However, in a preferred embodiment, each flange 52 includes a plurality of tab receiving openings 68. Each opening 68 has a shape that compliments and receives the locking tab 66 in a snug fashion. The triangular shape of tab 66 and the corresponding shape of opening 68 enhance the locking feature of locking system 64. The openings 68 are defined by spacers 69 that extend away from the flanges 52 in the direction of the interior of the container 10. In the present invention, the tabs 66 slide into the openings 68 as the sidewalls 34, 36 are pivoted from the collapsed position to the upright position and into engagement with the end walls 44, 46. The wall of each flange 52 provides a stop against the movement of the tabs 66. In an alternative embodiment, the tabs 66 could be located on the flanges 52 and the openings 68 arranged on flanges 54. When the tabs 66 are received in the openings 68, a first lock for the walls 34, 36, 44, 46 is established and the walls are not able to move laterally relative to one another.

As illustrated in FIG. 1, the container 10 also includes a wall guiding system 100. The guiding system 100 includes a male protrusion or spur 110 positioned along one of the flanges 54 of the sidewalls 34, 36. The spur 110 extends away from the side edge or face of its sidewall in the direction of a respective end wall that is parallel to the length of the sidewalls and perpendicular to the length of the end walls. As shown in FIG. 3, the spur 110 is secured to the flange/sidewall along only one edge so that it is free to be received by a complimentary female member on a cooperating end wall. Each spur 110 is spaced from the other portions of the flange 54 including the tabs 66 along its height.

As shown in FIGS. 10 and 11, each end wall 44, 46 also includes a portion of the guiding system 100 for receiving the spur 110 and aligning the mating portions of the locking system 64 of cooperating walls so that these walls can be easily and properly secured together when the sidewalls 34, 36 are raised as the end walls 44, 46 are in an upright position. The spur 110 is received and guided by an elongated guiding channel 120 formed by two coextensive, opposing, contoured members 125 that extend away from the inner surface or inner face of their end wall in the direction of the interior of the container 10 and substantially parallel to the length of the sidewalls 34, 36, as shown in FIGS. 10 and 13. The members 125 also extend along a portion of their respective end walls.

Each member 125 has an outer surface 126 that covers an inner, recessed track 127 in which the spur 110 travels as the sidewalls are raised during the assembly of the container 10. A wide, tapered opening 128 provides access to its respective track 127 so that the spur 110 of the cooperating sidewall will be easily and conveniently received within the channel 120 even if the sidewall is not properly aligned while it is being raised. This receipt of the spur 110 is also facilitated by the angled of flared orientation of the opening 128 relative to the remainder of the guiding channel 120. FIG. 11 illustrates that the sides of the opening 128 can be angled or flared in the direction that the spur 110 travels (the arc that the spur 110 sweeps) as its sidewall is raised so the spur 110 is easily and quickly received by the opening 128 and inserted into the guide channel 120. The spur 110 can also be angled or curved in the direction of the opening 128 for aiding in the fast and accurate alignment of the sidewalls and end walls.

In a preferred embodiment of the assembly of the container 10, the spur 110 includes two tabs 112 as shown in FIG. 6. As the sidewalls 34, 36 are rotated toward their upright position, their spurs 110 each move toward one of the guiding channels 120. When each spur 110 reaches its respective guiding channel 120, it is received in the opening 128 and its tabs 112 move along the tracks 127 behind members 125 prior to the sidewall coming to a vertical position. The members 125 prevent the sidewalls 34, 36 from moving relative to the end walls 44, 46 in the direction of the interior of the container 10. This increases the accuracy of the wall alignment and reduces the effort and time needed to lock the walls together in their upright positions. Similarly, the meshing of the spurs 110 and the guiding channels 120 pulls the corners of the container walls 34, 36, 44, 46 together so that a tight fit is created. The meshing also aligns the walls with each other so that a latching system 200 can securely hold them together with the minimum number of steps being performed. The spur 110 and the tracks 127 can have any cooperating shapes that permit the walls to be closely aligned as the flange 54 passes over the latching system 200 as discussed below. For example, the spur 110 could have an “L” shape and the tracks 127 a cooperating groove.

In an alternative embodiment, the placement of the spurs 110 and guiding channel 120 can be reversed. In this alternative embodiment, the spurs 110 extend from the flanges 52 and the guiding channels 120 are located on the sidewalls 34, 36.

As shown in FIG. 1, the container 10 also includes a plurality of wall latching systems 200 for releasably latching adjacent side and end walls together when the side and end walls are in their upright positions. Each wall latching system 200 includes a latching member 210 that is operatively mounted proximate the ends of each end wall 44, 46 near the flanges 52. As seen in FIG. 6, the latching system 200 also includes a latching surface 220 on an inwardly facing surface of a cooperating sidewall 34, 36. Each latching member 210 is formed of the same material as the container 10 and positioned within an opening 230 in its respective end wall. Each latching member 210 includes an inner or actuating face 215 that is on the side of the latching member 210 and its respective end wall that faces into the interior of the container 10. The actuating face 215 is contoured as shown in FIG. 10.

The latching members 210 are secured to their respective end wall along a single edge 211, see FIG. 9. As a result, the edge 211 including hole 244 forms a hinge region 212 about which latching member 210 flexes. The hole 244 helps to distribute the bending stresses created at edge 211 over the entire hinge region 212 so that the stresses are not localized and do not cause premature failure of the container 10. The plastic deformation of the material that forms the hinge region 212 allows the latching member 210 to flex in response to pressure that is applied to its inner face 215. As understood, this pressure can be caused by an operator pressing the latching member 210 in order to release the sidewall or by a flange 54 passing over the latching member 210 as the sidewall is being moved to its upright position, as discussed below. In an alternative embodiment, the biasing strength of the hinge that opposes movement of the latching member 210 is provided by a spring that acts on a rear or side surface of the latching member 210.

The latching member 210 includes a first portion 241 that is flat and coplanar with its respective end wall. The latching member 210 also includes a second portion 242 that is inclined toward a third portion 243. This inclined profile of the latching members 210 along their second portions 242 permit the sidewalls to be easily and smoothly raised from their folded positions to their upright positions as they pass over their respective latching members 210. As a sidewall is pivoted toward its upright position, a ribbed contact portion 220 of its flange 54 begins to contact the latching member 210 at the second portion 242. This contact causes the latching member 210 to begin to flex at the hinge region 212. However, contact with the second section 242 and flexion of the hinge 212 do not occur until after the spur 110 is received in its guide channel 120. As a result, latching member 210 will not be flexed until after the sidewall and cooperating end wall have been properly aligned.

As seen in FIG. 10, the second portion 242 extends away from its respective end wall in the direction of the interior of the container 10. The third portion 243 extends further into the interior of the container that does the second portion 242. Therefore, when the third portion 243 contacts the flange 54, it forces the hinge 212 to experience full flexion. At this point, the third portion 243 becomes flush with the inner surface of its end wall. When this occurs, the latching member 210 is deflected far enough away from the interior of the container and into opening 230 that the flange 54 can easily move past it and into a locking position. After the flange 54 has passed the latching member 210, the latching member 210 springs back into its original rest position and retains the latching surface 220 of the flange 54 behind it. When the latching surface 220 of the flange 54 is behind the latching member 210, its respective sidewall is stopped from moving relative to the other walls and toward the base 14.

The second portion 242 and the third portion 243 can also be deflected to the above-mentioned extent by depressing a recess 244, or other area, on the second section 242. When recess 244 is depressed by a person, it causes the hinge 212 to flex and the latching member 210 to move into opening 248. The more pressure applied to the latching member 210, the more deflection that the latching member 210 will experience. When third portion 243 is flush with the inner face of its end wall, the respective sidewall is free to rotate back toward the base 14 and into its folded position. According to the present invention, moving the sidewalls 34, 36 from their folded position to their upright position requires only sufficient force to drive the flanges 54 into the latching members 210 and deflect the latching members 210 until they are substantially flush with the inner surface of their respective end walls.

As shown in FIG. 9, the rear side 245 of the latching member 210 includes a deformation prevention member 250. The rear side 245 faces away from the interior of the container. In a preferred embodiment, the deformation prevention member 250 includes an arm 251 that extends away from the rear side 245. The arm 251 includes a terminal end 252 that is spaced far enough from a horizontally extending stop wall 246 that the latching member 210 can be flexed until third portion 243 is flush with the inner surface of its end wall. However, terminal end 252 is spaced close enough to wall 246 that the hinge 212 will not experience irreversible elastic deformation in response to pressure being applied to the latching member 210. The distance that the terminal end 252 will travel before contacting wall 246 is just slightly longer than the distance that the latching member 210 is deflected when a wall is locked upright or released for folding. In an alternative embodiment, the deformation prevention member is not on a rear surface of the latching member 210. Instead, it extends outwardly away from a rear surface of its respective end wall or sidewall and contacts the back of latching member 210 in order to prevent the hinge 212 from being bent to a point where it experiences irreversible deformation.

As shown in FIGS. 1 and 6, the top surfaces 43 of the sidewalls 34, 36 and the end walls 44, 46 are contoured. These surfaces 43 have a plurality of stacking tabs 58 that extend upwardly in a direction away from base 14 for being received in pockets 62. As shown in FIG. 2, the receiving pockets 62 are positioned along the bottom, outer edge of the base 14 so that the container 10 can be securely stacked on top of another container in ether a chimney stack or a cross stack pattern. As is well known in the art, chimney stacking includes positioning containers on top of each other so that they are all oriented in the same direction. Conversely, cross stacking includes stacking the containers so that containers from adjacent rows are oriented in alternate directions and containers from alternating rows are oriented in the same direction. The stacking tabs 58 and the receiving pockets 62 permit a user of these containers to interlock them while their walls are in an upright position. As a result, in either stacking pattern, a plurality of the stacking tabs 58 engage a corresponding number of receiving pockets 62 in order to prevent relative movement between the stacked containers.

In a preferred embodiment, the shape of the stacking tabs 58 and receiving pockets 62 is rectangular. However, any shape that can be used to securely stack containers on top of each other could be employed. Also, it is possible for the stacking tabs 58 to extend from the bottom of the base 14 and the receiving pockets to be positioned around the top surfaces. It is also possible for the container 10 to nest with other containers when the sidewalls 34, 36 and end walls 44, 46 are in folded positions.

As discussed above, the sidewalls 34, 36 can have any height. However, when the combined height of the sidewalls 34, 36 including their stacking tabs 58 is greater than the width of the base 14, as shown in FIG. 15, the top surface 43 of each sidewall 34, 36 includes recesses 56. These recesses 56 correspond to and receive the stacking tabs of the opposing sidewall when the sidewalls 34, 36 are folded. The recesses 56 eliminate the need for the sidewalls 34, 36 to be folded on top of each other. As a result, the folded height of the container 10 remains low because the height of the bottom panel 15 is not increased so that the end walls 44, 46 can be folded over the sidewalls 34, 36. The relationship between the stacking tabs 58 and the recesses 56 is clearly shown in FIGS. 1 and 15. The recesses 56 can also be used to receive other portions of an opposing sidewall. When the height of the sidewalls 34, 36 is less than the width of the base 14 and the stacking tabs 58 will not engage the opposing sidewall, the top surface 43 of each sidewall does not need to be notched as shown in FIGS. 15 and 16.

It is understood, of course, that while the forms of the invention herein shown and described include the best mode contemplated for carrying out the present invention, they are not intended to illustrate all possible forms thereof. It will also be understood that the words used are descriptive rather than limiting, and that various changes may be made without departing from the spirit or scope of the invention as claimed below. 

1. A self cooling container comprises a: horizontal floor portion, and four adjoining vertical wall portions, wherein at least one of the floor portion and four adjoining vertical wall portions are formed of a material having a high thermal conductivity.
 2. The self cooling container of claim 1, wherein the thermal conductivity of the material is substantially greater than that of polypropylene.
 3. The self cooling container of claim 1, wherein at least a respective pair of adjoining vertical walls are opposed from each other, each vertical wall of said respective pair being formed with vent openings therein.
 4. The self cooling container of claim 1, wherein a first and second wall of the four adjoining vertical walls are pivotally connected to the floor portion and a third and fourth wall of the four adjoining vertical walls are each pivotally connected to said floor portion.
 5. The self cooling container of claim 1, wherein the material having a high thermal conductivity has a thermal conductivity of about 0.30 W·K⁻¹·m⁻¹ to 1.2 W·K⁻¹·m⁻¹.
 6. The self cooling container of claim 1, wherein the material is a polypropylene resin mixed with exfoliated graphite.
 7. The self cooling container of claim 1, wherein the material having a high thermal conductivity has a thermal conductivity of between 0.39 W·K⁻¹·m⁻¹ and 0.8 W·K⁻¹·m⁻¹.
 8. The self cooling container of claim 1, wherein the material having a high thermal conductivity is a high density polyethylene resin mixed with exfoliated graphite.
 9. The self cooling container of claim 7, wherein the material is between five percent to thirty percent exfoliated graphite by weight.
 10. The self cooling container of claim 8, wherein the material is between five percent to thirty percent exfoliated graphite by weight.
 11. The self cooling container of claim 1, wherein the material having a high thermal conductivity is polypropylene mixed with exfoliated graphite, the exfoliated graphite being present at between about five percent to thirty percent by weight, and the thermal conductivity of the material being between about 0.30 W·K⁻¹·m⁻¹ to 1.2 W·K⁻¹·m⁻¹.
 12. The self cooling container of claim 1, wherein the material having a high thermal conductivity is a high density polyethylene resin mixed with exfoliated graphite, containing mixed exfoliated graphite by weight of between five percent and thirty percent, and the material having a thermal conductivity between 0.39 W·K⁻¹·m⁻¹ and 0.8 W·K⁻¹·m⁻¹. 